Porous Material and Method for Producing the Same

ABSTRACT

A method for making a composite and/or structured material includes: forming a lattice construction from a plurality of solid particles, the construction being formed so as to have one or more gaps between the particles; invading the lattice construction with a fluid material such that the fluid material at least partially penetrates the gaps; and, solidifying the material which invaded the lattice construction to form a composite material. In one suitable embodiment, the method further includes removing at least a portion of the lattice construction from the composite material thereby forming at the location of the removed portion one or more pores in the solidified material that invaded the construction.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation-In-Part and claims the benefitof U.S. application Ser. No. 12/997,343 filed Dec. 10, 2010, which is a371 of International Application No. PCT/US2009/047286 filed Jun. 12,2009, which claims priority to U.S. Provisional Application No.61/061,066 filed Jun. 12, 2008, all of which are incorporated herein intheir entireties.

BACKGROUND

The present inventive subject matter relates generally to the materialand/or material production arts. Particular relevance is found inconnection with composite and/or micro-structured polymeric materials,and accordingly the present specification makes specific referencethereto. However, it is to be appreciated that aspects of the presentinventive subject matter are also equally amenable to other likeapplications.

Polymeric materials and films are widely used for various productsand/or applications and have a broad range of properties that they candeliver at relatively low costs. In particular, polymeric surfaces canbe functionalized in order to exhibit desired properties for a specificapplication. For example, a polymeric surface can be altered physicallyand/or chemically in order to improve its printability, filtrationperformance, adhesion, wettability, weatherability, permeability,optical properties or incorporate specific functional groups.

Several techniques have been previously developed to createmicro-structures on and/or in polymeric materials. In particular,techniques have been previously developed to create porous or structuredpolymeric material by the formation of pores or other like structurestherein. See, e.g., U.S. Pat. No. 3,679,538 to Druin et al., U.S. Pat.No. 4,863,604 to Lo et al., U.S. Pat. No. 4,487,731 to Kobayashi, andU.S. Patent Application Pub. No. 2004/0026811 to Murphy et al., allincorporated in their entirety herein.

However, many prior developed techniques are generally limited in oneway or another. For example, some may only work for making porousstructures throughout the entire polymer. That is to say, there is alack control with regard to the extent of the micro-structure and/orpore formation and/or the connectivity there between. Additionally,prior developed techniques may be time consuming, complicated and/or notwell suited to conventional commercial production processes (e.g., suchas roll-to-roll polymer film production) which one may desire to use.

Micro-embossing, photolithography, etching, and laser drilling are amongother methods previously developed to generate texture andmicro-structures at or on the surface of polymers. While some of thesemethods are advantageous due to economical and technological issues,they generally lack the ability to efficiently and/or effectivelyproduce certain branched and/or closed loop structures. Additionally, ingeneral, they may not be well suited to the production of internalnetworks of interconnected pores.

Accordingly, new and/or improved micro-structured and/or compositematerial(s) and/or method(s) for producing the same are disclosed whichaddress the above-referenced problem(s) and/or others.

SUMMARY OF THE DISCLOSURE

According to one exemplary embodiment disclosed herein, a method isprovided for creating composite materials.

According to another exemplary embodiment disclosed herein, a method isprovided to create micro-structured polymeric materials. Suitably, themicrostructures include branched or closed loop microstructures atpolymeric surfaces, or throughout a polymer film.

According to another exemplary embodiment disclosed herein, a method isprovided that allows for substantial flexibility in the design of themicrostructures and which simplifies the elimination of a latticestructure used to form those microstructures.

According to another exemplary embodiment disclosed herein, a method isprovided that allows suitable control of pore creation in a material,including control of the pore size, pore-size distribution and/or poreconnectivity. Suitably, the pore-size distribution can be narrow orbroad, uni- or multi-modal. Optionally, the pores can be uniform orgraded in distribution in the cross-section and/or face of the film.Moreover, each layer defined by the pore size can be uniform or graded.

One embodiment disclosed herein relates to a novel method to createcomposite materials using the concept of fluid flow and fluid displacingin a lattice construction. The lattice construction can be consolidated(i.e., the matrix particles are connected) or unconsolidated (i.e., madeof individual particles that can freely move but held in place bycompaction or by other means, such as liquid surface tension). Suitably,an invading fluid, for example a polymeric material, is used to displacethe fluids (e.g., air) in the lattice construction. Depending on thenetwork geometry of lattice construction, the physical properties of thefluid existing in the lattice construction and the displacing fluid,various flow patterns with different topology can be achieved (see FIG.43). For example, in imbibition, in which a wetting fluid displaces anon-wetting fluid, a three dimensional flow pattern with closed loopsare generated (called imbibition cluster). While drainage, where anon-wetting fluid displaces a wetting fluid, generates a totallydifferent three-dimensional branching structure (called drainagecluster) without closed loops (FIG. 43).

Suitably, the invading fluid can be optionally solidified inside of thelattice construction by any means to form a composite material. Forexample, the invading fluid can be solidified by cooling or curing. Theoriginal lattice construction may remain part of the finished compositematerial in order to provide specific functions. Alternately, thelattice construction may be a sacrificial component which can be removedafter the polymer microstructure is formed. Suitably, the optionallydisplaced and/or original fluid in the lattice construction can be anyfluid, for example it can be any gas including air, or any liquid thatcan optionally be solidified, or a mixture of gas and liquid (i.e.,foam). In one suitable embodiment, the fluid that originally exists inthe lattice construction is displaced at least partially with theinvading fluid. Any remaining part of the original fluid can be eitheroptionally removed or left in the final composite material. In the latercase, the remaining original fluid can be optionally solidified by anymeans.

According to another exemplary embodiment disclosed herein, a processfor producing a composite and/or structured material includes the stepsof: forming a lattice construction, fluidization of a polymericmaterial, invasion of the polymeric material into the latticeconstruction and solidification of the resulting polymer composite.Additionally, there can be an optional step of removing at least aportion of the lattice construction. Suitably, these steps can beseparate steps, but alternately, they can be performed simultaneously aswell.

According to yet another exemplary embodiment disclosed herein, thelattice construction is formed by packing granular solids that are atleast partially soluble in certain solvents. Optionally, the solids canbe a mixture of solid particles of different chemical nature, sizeand/or shape. Suitably, the solids can be milled (ground) in a firstnon-solvent liquid. AN optional filtering process can be used followingthe milling to narrow the particle size of the solids. Optionally, themilling liquid can be evaporated and/or dried off at this point.Suitably, a second liquid can be introduced to re-disperse the solidparticles to form a homogenous solid suspension. This second suspendingliquid may or may not be the same as the first milling liquid. Suitably,the solid suspension is then coated onto a substrate or surface, e.g.,via die or pattern coating, spraying, screen, gravure or ink-jetprinting or other like application or deposition methods. Optionally,the suspension liquid can then be dried off to leave a cake of granularsolids on the substrate. The cake of granular solids functions as thelattice construction in later steps. In another method, the solids canbe dry-milled in a controlled environment (e.g., temperature andhumidity controlled) and subsequently compacted to form the cake.

In one disclosed embodiment, the invading fluid, for example a polymer,is put in contact with the lattice construction so that the fluidinvades into the gaps, voids and/or spaces between particles of thelattice construction. Suitably, the invading fluid is a polymericsolution, which can be dried later on or precipitated by another liquid,or in liquid forms which can be cured later on, or be vapor deposited,or solidified by cooling. The invading fluid is then solidified andoptionally separated from the lattice construction. The residual solidsfrom the lattice construction remaining on the solidified invadingmaterial can then be either washed off or left behind, leaving amaterial with a porous structure or a structured composite.

In alternate embodiments, the process disclosed herein can be used tocreate composite and/or porous structures on one side or both sides of amaterial, or throughout the whole thickness of the material. Moreover,the extent of the composite layer on the film surface can be partial orfull, and the size and extent of coverage can be regular or random.

In accordance with alternate embodiments disclosed herein, the invadingpolymer material can be a preformed film or liquid. Optionally, the filmcan be stretched uniaxially, bi-axially or unstretched; the polymer filmcan be extruded; the polymer film can be single layer or multilayer; amultilayer film can be created by lamination or coextrusion; and/or, thepolymer film can have one or more fillers in it.

In any event, numerous advantages and benefits of the inventive subjectmatter disclosed herein will become apparent to those of ordinary skillin the art upon reading and understanding the present specification.

BRIEF DESCRIPTION OF THE DRAWINGS

The inventive subject matter disclosed herein may take form in variouscomponents and arrangements of components, and in various steps andarrangements of steps. The drawings are only for purposes ofillustrating preferred embodiments and are not to be construed aslimiting. Further, it is to be appreciated that the drawings may not beto scale.

FIG. 1 is a flow chart illustrating an exemplary process for producingcomposite and/or structured/porous material in accordance with aspectsof the present inventive subject matter.

FIG. 2 is a schematic diagram showing different materials, constructionsand the like formed at various steps in the process disclosed herein.

FIG. 3 is a schematic diagram showing a corresponding latticeconstruction, composite material and final structured/porous materialformed in conjunction with the presently disclosed process.

FIG. 4 a schematic diagram showing a more specific exemplary process forproducing composite and/or structured/porous material in accordance withaspects of the present inventive subject matter.

FIG. 5 is an SEM (Scanning Electron Microscope) image showing incross-section a material produced in accordance with aspects of thepresent inventive subject matter, said material being a porous compositematerial encapsulating a functional particle, namely, a silver coatedglass bead.

FIG. 6 is a schematic diagram showing an exemplary apparatus for carryout an exemplary material production process as disclosed herein.

FIG. 7 is a graph illustrating an exemplary particle size-distributionof a slurry used to prepare lattice constructions in accordance withaspects of the present inventive subject matter.

FIG. 8 is a schematic diagram showing an exemplary set-up used inexperiments to prepare sample materials in accordance with aspects ofthe present inventive subject matter.

FIGS. 9A, 9B and 9C are a table showing processing parameters used forseveral experiments in which sample materials were prepared inaccordance with aspects of the present inventive subject matter.

FIGS. 10-39 are SEM images showing top and cross-section views ofvarious sample materials prepared in accordance with aspects of thepresent inventive subject matter.

FIG. 14A is a magnified SEM image of a portion of FIG. 14.

FIG. 15A is a magnified SEM image of a portion of FIG. 15.

FIG. 40 is a graph illustrating the percentage light transmission of amaterial as a function of the thickness of a porous layer formed thereinin accordance with aspects of the present inventive subject matter.

FIG. 41 is a graph illustrating the clarity of a material as a functionof the thickness of a porous layer formed therein in accordance withaspects of the present inventive subject matter.

FIG. 42 is a graph illustrating the haze of a material as a function ofthe thickness of a porous layer formed therein in accordance withaspects of the present inventive subject matter.

FIG. 43 represents the various types of clusters that can be formedduring the invasion process (imbibition or drainage) [Taken from J.Phys: Conden. Matter. 2, SA79, (1990)].

FIG. 44 shows the variations of the process to make layered, patterned,and gradient structures.

DETAILED DESCRIPTION

For clarity and simplicity, the present specification shall refer tostructural and/or functional elements, relevant standards and/orprotocols, and other components that are commonly known in the artwithout further detailed explanation as to their configuration oroperation except to the extent they have been modified or altered inaccordance with and/or to accommodate the preferred embodiment(s)presented herein. Additionally, unless otherwise specified, as usedherein: the terms micro, micro-sized and the like refer to elements orfeatures having dimensions on the order of micrometers; the term fluidor the like refers to a flowable liquid or gas or other flowablematerial; the term composite or the like refers to a material that ismade of two or more component materials which differ in chemical and/orphysical properties (e.g., a composite may be made of a polymericmaterial and a solid or a fluid (including air)); the termsuperhydrophobic when used in reference to materials and/or surfacesmeans materials and/or surfaces that are extremely difficult to wet,i.e., having water contact angles in excess of 150°; the termsuperoleophobic when used in reference to materials and/or surfacesmeans materials and/or surfaces that display contact angles greater than150° with respect to organic liquids; the Cassie Baxter state refers tothe case when a droplet or liquid is resting partly on the raisedfeature(s) or asperities of a solid material and bridging the gap(s)there between; and, the term fouling or the like refers to theaccumulation and/or deposition of living organisms and certainnon-living material on hard surfaces (e.g., filters and membranes).Additionally, numeric or other values, quantities, ranges, dimensions,temperatures, time periods, weights, percentages, ratios and the likereferred to herein are meant to be approximate, unless otherwiseindicated.

In general, the present specification discloses various embodiments of amaterial, e.g., an at least partially polymeric material. In oneexemplary embodiment, the disclosed material is optionally a compositematerial including a plurality of different component materials, e.g.,including at least one polymeric component. In another exemplaryembodiment, the disclosed material selectively has one or moremicro-sized structures formed therein and/or thereon. Suitably, themicro-sized structures are pores or other like spaces, gaps or voidsformed within the material. In selected exemplary embodiments, the poresare optionally in fluid communication with one another so as to form aninterconnected network of pores within the material. The presentspecification also discloses an inventive method(s) for fabrication ofthe aforementioned materials. In one suitable process, a compositematerial is first formed as an intermediate material. Subsequently, atleast a portion of at least one of the component materials making up thecomposite is removed to form the final structured material, e.g., withpores remaining where the removed material previously resided.

With reference now to FIGS. 1 and 2, there is now described an exemplaryprocess for making a composite and/or micro-structure containingmaterial according to aspects of the present inventive subject matter.In particular, FIG. 1 depicts a flow chart illustrating an exemplaryprocess for making the aforementioned material(s), and FIG. 2illustrates the materials and/or intermediate constructions formed atvarious points or stages within the process.

In a first step 100 (see FIG. 1), a lattice construction 10 (e.g., asseen in FIG. 2) is prepared. In particular, the construction 10 issuitably a one, two or three dimensional lattice or framework of solidparticles 10 a (i.e., grains of material). As shown in FIG. 2, thelattice includes an irregular geometric arrangement of the particles 10a, however alternately, the particles 10 a may have a regular geometricarrangement within the lattice. Suitably, as shown in FIG. 2, certainparticles 10 a abut, contact or otherwise touch one or more of theirneighboring particles 10 a while forming one or more voids, gaps orspaces between the respective particles 10 a (i.e., regions where theparticles 10 a do not exist or reside).

In one exemplary embodiment, each particle 10 a is optionally made ofthe same material. However, in alternate embodiments, the respectiveparticles 10 a may be made from a plurality of different materials.Suitably, the granular solids used to produce the lattice construction10 can be one or more of any inorganic or organic solid material, e.g.,including salts, sugars, polymers, metals, etc. Optionally, where aportion of the lattice construction 10 is to be ultimately removed asdescribed below, the material to be removed is suitably chosen to be aselectively soluble material with respect to a given solvent.Conversely, where a portion of the lattice construction 10 is to remain,the material to remain is suitably chosen to be insoluble with respectto the given solvent.

As seen in FIG. 2, in one optional embodiment, during, upon or after itsformation, the lattice construction 10 is optionally infiltratedpartially or completely by a first fluid material 12 (e.g., which may beair or another fluid). That is to say, the first fluid material 12 atleast partially fills the spaces, voids and/or gaps between theparticles 10 a.

In a second step 200 (see FIG. 1), the lattice construction 10 iscompletely or partially invaded by a second fluid material 14. That isto say, the invading fluid 14 at least partially fills the spaces, voidsand/or gaps between the particles 10 a. Suitably, where the latticeconstruction 10 had been previously infiltrated by the fluid 12,optionally, the fluid 14 displaces some or all of the fluid 12. Inaddition to and/or in lieu of the aforementioned partial or completedisplacement, the fluid 14 may optionally mix or otherwise combine withsome or all of the fluid 12. Optionally, the invading fluid material 14is, e.g., a molten polymer, a monomer, a polymeric solution or the like.

In a third step 300 (see FIG. 1), the material 14 is suitably solidifiedthereby forming an intermediate composite material 16 including, e.g.,the solidified material 14, the lattice construction 10 and anyremaining amount of the material 12. Optionally, the aforementionedsolidification is achieved, e.g., via cooling of the material 14, curingof the material 14 using heat, light or otherwise, reaction of thematerial 14 with the material 12 and/or the material used to create thelattice construction 10, etc. Optionally, in forming the composite, anyremain fluid material 12 may also be solidified.

In an optional fourth step 400 (see FIG. 1), some or all of the materialmaking up the lattice construction 10 and/or any remaining first fluid12 is removed from the intermediate composite material 16 to create thefinal structured material 18. In particular, the removed portions of thelattice construction 10 and/or any remaining first fluid 12 in effectform or leave behind one or more micro-structures (e.g., a network ofinterconnected pores) in the final structured material 18. Optionally,the aforementioned removal process may be performed, e.g., bydissolving, washing, etching, vaporizing or volatilizing away theremoved portions or by other like techniques.

With further reference now to FIG. 2, there is shown various materials,constructions and/or intermediate composites at a plurality of stages inthe aforementioned fabrication process. Note, various optionalembodiments and/or scenarios are depicted in FIG. 2. In particular,stages labeled with reference characters having like numeric valuesrepresent like stages in the production process, while those likenumerically referenced stages having different alphabetic valuesrepresent different alternate options, scenarios and/or embodiments.

At the stages labeled 102 a and 102 b, a suitable lattice construction10 made of solid particles 10 a is present. As shown in stage 102 a, thewhite or un-shaded region(s) represent the spaces, voids or gaps betweenthe particles 10 a. In general, as shown in FIG. 2, the white orun-shaded region(s) represents the absence of particles 10 a, material12 and/or material 14. As depicted in stage 102 b as compared to stage102 a, the lattice construction 10 is shown being optionally infiltratedwith the fluid material 12, indicated generally in FIG. 2 by the lightgrey shaded region(s). At the stages labeled 202 a and 202 b, there isshown the invasion of the fluid material 14, indicated generally in FIG.2 by the dark grey shaded region(s).

The stages labeled 302 a, 302 b and 302 c, show embodiments of theintermediate composite material 16. Suitably, as shown in the stagelabeled 302 a, the material 14 only partially invades the latticeconstruction 10 (see, e.g., the remaining white or un-shaded regions inthe composite material 16). As shown in the stage labeled 302 b, thematerial 14 again only partially invades the lattice construction 10thereby leaving a portion of the material 12 un-displaced (see, e.g.,the remaining light grey shaded regions in the composite material 16).Alternately, as shown in the stage labeled 302 c, the material 14 hassubstantially completely invaded the lattice construction 10, therebyfilling essentially all the voids, spaces and/or gaps between theparticles 10 a and/or displacing essentially all the fluid material 12.In all three cases, however, the intermediate composite material 16 isnow formed, e.g., upon solidification of the material 14.

Finally, the stages labeled 402 a, 402 b and 402 c show the finalstructured (i.e., porous) material 18 resulting from removal of thelattice construction 10 from the intermediate composite materials 16depicted in each of the stages 302 a, 302 b and 302 c, respectively.

With reference now to FIG. 3, there is shown corresponding examples of alattice construction 10 formed of particles 10 a, a compositeintermediate material 16 formed by the invasion of material 14 into thelattice construction 10, and the resulting final structured/porousmaterial 18 obtained by the removal of the lattice construction 10. FromFIG. 3, it can be appreciated that the pore size distribution and poreconnectivity in the final structured material 18 can be selectivecontrolled largely by the size distribution of the granular solids orparticles 10 a, their shapes, and the way they are packed and/orarranged in the lattice construction 10. As shown in FIG. 3, the porespace of the material 18 is generally dividable into pore bodies 18 aand pore throats 18 b. The bodies 18 a are represented by the relativelylarge voids or spaces or volumes that are generally created or formed,e.g., by removing the granular solids or particles 10 a, while therelatively narrow channels or throats 18 b providing fluid communicationand/or connectivity between pore bodies 18 a are generally created orformed where the particles 10 a contacted one another and/or by any voidspace around the contact areas that was not penetrated by the fluidmaterial 14. For the most part, the porosity in general of the finalmaterial 18 is dependent on the size distribution and/or quantity of thepore bodies 18 a, whereas fluid flow properties of the final material 18are controlled by the throats 18 b.

As already pointed out, the size distribution and/or quantity of thepore bodies 18 a is related to the size distribution and/or quantity ofthe granular solids and/or particles 10 a in the original latticeconstruction 10, while the size distribution of the pore throats 18 b issimilarly related to the contact areas between the particles 10 a. Sincethe size distribution of the particles 10 a can be readily controlledand/or measured before the lattice construction 10 is fabricated, this apriori information is known data. Accordingly, from this a prior data,the size distribution of the pore bodies 18 a (and thus the effectiveporosity of the material 18) can also be known, calculated or closelyestimated a priori, i.e., prior to the actual formation of the finalmaterial 18. Likewise, the size distribution of the contact areasbetween the granular solids or particles 10 a depends on the degree ofcompaction of the particles 10 a and the roundness around their corners,as well as their shapes. Given the size distribution of the particles 10a, the degree of compaction, their shapes, etc., one can determine thesize distribution of the contact areas between the particles 10 a (e.g.,by computer simulation or otherwise) and, hence, the size distributionof the resulting pore throats 18 b. Thus, the relevant information onthe morphology of the resulting pore space in the final material 18 canbe known a priori, i.e., before the material 18 is even fabricated.

With reference now to FIG. 4, one exemplary embodiment for fabricating amaterial in accordance with aspects of the present inventive subjectmatter will now be described. In relation to the higher level processdescribed with reference to FIG. 1, it is to be noted that: steps110-118 illustrated in FIG. 4 are sub-steps correspond to the over-allstep 100 illustrated in FIG. 1; steps 210 and 212 illustrated in FIG. 4are sub-steps correspond to the over-all step 200 illustrated in FIG. 1;step 310 illustrated in FIG. 4 is a sub-step correspond to the over-allstep 300 illustrated in FIG. 1; and, optional steps 410 and 412illustrated in FIG. 4 are sub-steps correspond to the over-all step 400illustrated in FIG. 1.

As illustrated in FIG. 4, the process begins at step 110 with a salt orother granular solid material. At step 112, the granular material fromstep 110 is milled or otherwise ground to achieve particles 10 a of adesired size and/or shape. Optionally, the solids can be dry-milled ormilled in a non-solvent liquid. For example, if granular NaCl is used toform the lattice construction 10, then isopropyl alcohol (IPA) is asuitable milling liquid. If wet-milling is performed, optionally oncethe wet-milling is complete, a drying or other like step can bepreformed to evaporate or otherwise remove the milling liquid from theproduced particles 10 a. Alternately, other methods can be used toproduce the desired particles 10 a. For example, they can be formed byprecipitation from a solution or recrystallization. In this case, thesize and/or shape of the particles 10 a is optionally controlled by theprocessing conditions (e.g., temperature, mixing conditions, etc.) atwhich the precipitation and/or recrystallization is conducted.Additionally, in either case, particle-size distribution can further becontrolled, e.g., by filtering or sieving.

Optionally, one or more granular solid materials may be used to createthe lattice construction 10. Likewise, one or more shapes and/or sizesof particles 10 a may optionally be employed to achieve a desiredparticle-size distribution. The selected size(s), shape(s) and/ormaterial(s) depend on the intermediate composite material and/or finalstructured/porous material which is ultimately desired. Examples ofgranular solids than may be used include but are not limited to, e.g.,CaCO3, NaCl, KCI, Na2SO4, Na2S2O5, etc. In general, the granular solidcan be a mixture of solid particles of different chemical nature, sizeand shape. The granular solid can be a soluble material in a givensolvent or solvent mixture. Optionally, the granular solid may containmaterials that are not soluble in a particular solvent. For example, agranular solid can be a mixture of sodium chloride (i.e., water soluble)and titanium dioxide (i.e., water insoluble) powders.

At step 114, the granular medium from step 112 is mixed in a suspendingliquid, which may or may not be the same as the milling liquid. Forexample, suitable milling and/or suspension fluids include but are notlimited to, e.g., air, alcohols (IPA, propylene glycol, ethylene glycol,glycerin, etc.), esters, ketones, aromatics, aliphatics, liquidpolymers, etc. Suitably, in the suspending liquid, the solid particles10 a are dispersed to form a substantially homogenous solid suspension.

At step 116, the liquid carrying the granular medium is then optionallyprinted, coated, deposited or otherwise applied to a surface orsubstrate. For example, such methods as die or pattern coating,spraying, screen, gravure or ink-jet printing, etc. may optionally beused. In particular, using a printing or pattern coating process has theadvantage that the liquid carrying the granular medium may beselectively deposited or applied in a desired pattern on the substrate,and accordingly, the lattice construction 10 is therefore formed only inthose places corresponding the deposition or application pattern.Consequently, the intermediate composite material 16 and/or the finalstructured/porous material 18 will likewise reflect the pattern. That isto say, the intermediate composite material 16 will have the latticeconstruction 10 formed therein in accordance with the pattern in whichliquid carrying the granular medium was deposited. Likewise, the finalstructured material 18 will have a patterned porosity corresponding tothe pattern in which liquid carrying the granular medium was deposited.In particular, the final structured material 18 will be made porous inthose areas corresponding to where the liquid carrying the granularmedium was deposited on the surface or substrate, while remainingnon-porous in those areas corresponding to where the liquid carrying thegranular medium was not deposited on the surface or substrate (FIG. 44).

At step 118, the coating is optionally dried, e.g., to evaporate orotherwise remove the suspending liquid, thereby leaving behind a latticeof the granular medium in the form of a cake or other like construction10 with spaces, voids and/or gaps defined between the respective grainsor particles 10 a. Optionally, in an alternate example, the latticeconstruction 10 can be formed by any other techniques known to peopleskilled in the art. One such example is to deposit the solids granulesor particles 10 a layer-by-layer or otherwise into a desired arrangementwithout the use of any liquid. In any event, the lattice construction 10formed from the granular solid can suitably have any desired shape orform. For example, the lattice construction 10 can be applied to thesurface or substrate uniformly or partially. In the latter case, thepartial coverage can be random or patterned. In short, any of variousspatial combinations of granular solids are contemplated.

At step 210, the invading fluid material 14 is applied or otherwisebrought into contact with the lattice construction 10. Optionally, theinvading fluid 14, i.e., the fluid that enters into the voids, spacesand/or gaps between the particles 10 a, can be made of any material. Inan exemplary embodiment, the invading fluid 14 is made of materials thatcan be at least partially solidified by suitable physical and/orchemical methods. For example, the invading fluid 14 can be a moltenpolymer, a monomer, a polymeric solution, etc. Optionally, the polymercan be deposited from the vapor phase. The polymer can be melted withconductive heating, microwave heating, infrared heating, or any othersuitable heating methods. Suitably, the polymer is introduced as apre-formed film or extruded onto the lattice construction 10. Thepolymers used for the invading material 14 include any one or more typesof material that are suitable for the process. For example, anythermoplastics, thermosets, monolayer films, laminated or coextrudedmultilayer films can be used. The polymers may also optionally containfillers. Examples of suitable polymers include acrylic polymers,glycol-modified polyethylene terephthalate (PETG), polypropelene (PP),PMMA, Nylon, Kraton rubbers, TiO2-filled KRATON-G 2832 (from KratonPolymers, Houston, Tex.), polyurethane thermoplastic elastomer, SURLYNionomer from DuPont (DuPont, Wilmington, Del.), polyethylene (PE),low-density polyethylene (LDPE), linear low-density polyethylene(LLDPE), polystyrene (PS), TPX (polymethylpentene, from Mitsui, Japan),polycarbonate, and polyolefins, high-performance films such aspolysulfone, polyethersulfone, fluoropolymers such as polyvinylidenefluoride (PVDF), perfluoroalkoxy fluopolyer (PFA), fluorinated ethylenepropylene (FEP) Teflon (DuPont, Wilmington, Del.), hydrophilic polymersuch as ethylene vinyl alcohol copolymer (EVOH), polyvinyl alcohol(PVA); biodegradable polymers such as polylactic acid (PLA),poly(dl-lactic acid) (P dl-LA), poly(l-lactic acid) (P I-LA),polycaprolactone (PCL), poly(glycolic acid) (PGA),poly(lactide-co-glycolide) (PLG), poly ((−)3-hydroxybutyric acid) (PHB);and the mixtures thereof.

At step 212, FIG. 4 shows the invasion of the fluid material 14 into thelattice construction. That is to say, the invading fluid 14 at leastpartially fills the spaces, voids and/or gaps between the particles 10a. Optionally, the lattice construction 10 may already contain anotherfluid 12, for example it may contain any gas including air or otherliquids, or it may be held under vacuum. Of course, if the latticeconstruction 10 already contains another fluid 12, the invading fluid 14enters into the spaces or gaps in the lattice construction 10 andoptionally displaces the fluid 12. Several parameters control theinvasion process and the final microstructure of different components(10, 12, and 14) including the differential pressure, capillarypressure, temperature, gravitational forces, wettability, surfacetension of various components, miscibility of fluids (12 and 14),reactivity, phase change, etc. Suitably, heated rollers, laminators, hotpresses and/or the like are used to provide the appropriate pressureand/or temperature that is desired to facilitate the invasion of thematerial 14 into the lattice construction 10. Optionally, the invadingfluid 14 can also be coated onto the lattice construction 10 throughslot die coating.

As shown in step 310 of FIG. 4, during the invasion process or upon itscompletion, various components including invading fluid 14 and/or anyremaining fluid 12 are at least partially solidified. Depending on thecomposition of the invading fluid 14 and/or the fluid 12, thesolidification process optionally includes the application of heat,light or cooling. For example, the cooling process is optionallyconducted by applying cold water or steam. Suitably, the cooling wateror steam is recycled using reverse osmosis, followed by evaporation. Forexample, the solidification of a polymer material 14 is optionallyachieved: through cooling by applying water at temperatures below themelting point (e.g., in the range of approximately 32-100° F.); throughcuring by ultraviolet (UV) radiation; through heating by other radiationsources (e.g., such as infrared (IR) or near-IR); through curing byapplication of steam; etc.

In one exemplary embodiment, the fluid 14 and fluid 12 optionally reactwith each other to form another material, e.g., which is at leastpartially solid. For example, fluid 14 can contain monomers such asacrylates and epoxies which can react and solidify upon contact withfluid 12, which contains curing agents such as peroxides or amines. Inanother example, fluid 14 and fluid 12 can contain positively- andnegatively-charged polyelectrolytes, which react upon contact to form aninsoluble complex.

In another exemplary embodiment, either the fluid 14, fluid 12 or bothcan react with the lattice construction 10. As an example, the latticeconstruction 10 is optionally made of a dry or solidified curing agentand the fluid 14, fluid 12 or both contain monomers that react with thecuring agent. In yet another example, the lattice construction can bemade of bivalent ionic salts such as magnesium or zinc oxides and fluid14, fluid 12 or both contain negatively-charged polyelectrolytes (e.g.,polyacrylic acid), such that the reaction there between results in asolid insoluble polyacrylic acid-zinc salt.

In still another embodiment, the fluid 14 and the fluid 12 can bepartially miscible fluids which phase separate upon contact. Forexample, fluid 14 can be an alcoholic solution of polyvinylbutyal whichphase separates upon mixing with water (i.e., fluid 12). Furthermore,the phase separation can be such that, the final precipitated phase havea micellar, lamellar, hexagonal, or bicontinuous structure. As a furtherexample, the fluid 14 can also contain oils or silanes which form amicellar, lamellar, or bicontinuous phase upon mixing withwater-nonionic (amphiphilic block copolymer, Pluronic F127, BASF)surfactant mixtures.

In any event, upon the completion of step 310, the intermediatecomposite material 16 has been achieved. Suitably, the process may endhere if the intermediate composite material 16 is the desire productionoutput. Alternately, however, additional steps 410 and 412 mayoptionally be carried out to remove at least a portion of at least oneof the composite material components as desired, e.g., to obtain amicrostructured and/or porous final material 18.

Optionally, the lattice construction 10 is at least partially removedfrom the composite material 16 produced in step 310. Of course, in onesuitable embodiment, the lattice construction 10 is substantiallyremoved in its entirety. Suitably, the removal process (e.g., steps 410and 412) involves dissolving, washing, etching, vaporizing and/orvolatilizing away the unwanted portion of the lattice construction 10.Alternately, other known method can be used remove or eliminate theunwanted portion of the lattice construction 10.

If the lattice construction 10 is only removed partially, the remainingpart may optionally have a specific function in the final composite. Forexample, the original lattice construction 10 may optionally containsome active material such as catalyst particles (e.g., platinumparticles) or antimicrobial agents (e.g., silver particles). Suitably,the catalyst particles or antimicrobial agents may be left behind in thefinal composite 18 after partial removal of the lattice construction 10.For example, FIG. 5 shows a composite material 18 made of polypropyleneand silver coated glass beads 20. In production, the silver coated glassbeads were originally mixed with salt particles to make the latticeconstruction 10. The polypropylene was then invaded into the salt andsilver coated glass bead lattice construction 10. After solidification,the salt particles were washed away, leaving the silver coated glassbeads in the final composite 18. In part due to its large size compareto the salt particles (which in general determined the size of the porescreated in the polypropylene) and also its insolubility in the washingliquid, the silver coated beads remained in the final composite 18.

In any event, as shown in FIG. 4, at step 410 the composite material 16is washed in a solvent or other like liquid or fluid material to removethe unwanted portion of the lattice construction 10 therefrom. Finally,a dry step (i.e., step 412) is optionally executed to evaporate orotherwise remove or eliminate any remaining washing fluid, therebyleaving the final structured/porous material 18.

With reference now to FIG. 6, there is illustrated a schematic diagramof an exemplary apparatus for carrying out the production processdescribed herein. As illustrated, an extruder 50 outputs a film ofmolten polymer (i.e., the fluid material 14) which is routed between twopressure rollers 62 of a press 60. Suitably, each pressure roller 62 hasformed on an outer surface thereof a lattice construction 10. As shown,to form the lattice construction 10 on each pressure roller 62, acoating roller 64 coats the pressure roll 62 with a liquid or fluid 66containing a solid suspension of the granular material which is to formthe lattice construction 10. After the liquid or fluid 66 containing thesolid suspension is coated on the pressure roller, the liquid or fluidis evaporate, dried off or otherwise removed to leave behind the latticeconstruction 10 on the outer surface of the pressure roller 62.

Upon passing between the pressure rollers 62, the molten polymer (i.e.,fluid material 14) is pressed and/or flowed into the latticeconstructions 10 on the surface of either pressure roller 62. That is tosay, the material 14 invades the lattice constructions 10, e.g., aspreviously described. As the film advances out from between the pressurerollers 62, the lattice constructions 10 are carried therewith havingbeen invaded by and/or embedded in the molten polymer. Accordingly, uponexiting the press 60, a web of composite material 16 is formed includingthe polymer material 14, e.g., which is suitably solidified and whichnow contains the lattice constructions 10 picked-up from the pressurerollers 62.

As shown in FIG. 6, the web of composite material 16 is then routedthrough a washing station 70, where it is sprayed, washed and/orotherwise treated to remove some portion or substantially all of thelattice construction 10. In particular, the washing liquid or fluid 72applied in the washing station 70 is optionally a solvent that dissolvesthe unwanted portion of the lattice construction 10. Suitably, afterpassing through the washing station 70, the web is then routed through adrying station or oven 80 which dries the web and/or evaporates off anyremaining washing fluid, thereby leaving a web of structured/porousmaterial 18. Finally, the web of structured/porous material 18 is thenwound on a roll 90. Of course, where the composite material 16 is thedesired production output, the washing station 70 and/or oven 80 mayoptionally be omitted or bypassed.

As can be appreciated from the above example, the extruded film wasprocessed on both sides thereof resulting in an intermediate compositematerial 16 with lattice constructions on both sides thereof and a finalstructured film material 18 with pores formed on both sides thereof.Alternately, only one side of the film may be so processed consequentlyresulting in composite material 16 with only one side containing thelattice construction 10 and/or a final structured material 18 have onlyone porous side. Additionally, as previously mentioned, the suspensionliquid or fluid 66 (i.e., containing the solid suspension of granularmaterial that is to make-up the lattice construction 10) is optionallypattern coated, printed or otherwise selectively applied to the surfaceof the pressure rollers 62 so that the lattice construction 10 is formedin accordance with the pattern and the resulting composite material 16and/or structured material 18 reflect that same pattern. Additionally,it is to be appreciated that the lattice construction 10 can remainand/or pores can be created a various depths within the film, e.g., theycan range anywhere from essentially mere surface features or maypenetrate the entire thickness of the film. For example, by controllingthe pressure between the rollers 62 and/or the weight and/or thicknessof the coating on the rollers 62 (and hence the height of the formedlattice construction 10), one can likewise control the depth to whichthe lattice construction 10 penetrates the film and/or the depth atwhich pores are formed.

In one exemplary embodiment, the lattice construction 10 is optionallyformed or otherwise arranged so that the granule or particle size orsize-distribution or the like progressively varies with respect to thedepth or height of the lattice construction 10. For example, such agradient may be achieve by applying a number of successive coatings tothe pressure roller 62 to build up the lattice construction 10, whereeach successive coating contains a solid suspension of granules orparticles having a somewhat larger or smaller size or size-distributionas compared to the prior coating. In turn, such a lattice construction10 produces a film or material 18 which has a corresponding gradient ofporosity across its thickness.

In any event, as described above, when employing the techniquesdescribed herein to produce the porous material 18, the relevantinformation on the morphology of the pore space can be known a priori,i.e., before the porous material 18 is even fabricated. This lead tosome significant results. For example, because one has substantiallycomplete information on the pore space morphology, one does not have touse such methods as the nitrogen adsorption (BET), mercury porosimetry,flow permporometry, etc., in order to determine what is classicallycalled the pore size distribution which is, in fact, the sizedistribution of the narrow channels. This is advantageous insomuch assuch methods either do not provide complete information, or are limitedto certain size ranges. Additionally, the present techniques offerconsiderable flexibility. That is to say, one can design any desiredsize distribution by selecting the appropriate particle shape and sizedistribution. Such control is particularly valuable to applicationsinvolving the passage of a fluid through the porous material 18. Thesize of the granular solids—that is, the size of the pore bodies—can becontrolled, so that the desired particle size distribution is obtained.As already stated, a granular solid having a desired size-distributionand particle shapes can be prepared by precipitation orrecrystallization. For example, if a salt is dissolved in water first tomake a salt solution, then the solution is added to a nonsolvent (suchas acetone), the salt starts to precipitate. By controlling the amountof salt solution, the temperature and other thermodynamic factors, aswell as the mixing conditions, one can obtain a wide range of sizes forthe salt crystals. The size of the pore throats may also be selectivelycontrolled and/or varied. For example, by adding a small amount of anonvolatile (high boiling point) liquid (such as propylene glycol,glycerin, etc.), or a water-soluble polymer (such as polyethyleneglycol, polyethylene oxide, etc.) to the solvent, then, upon drying, theadded liquid or water-soluble polymer will make bridges in the contactarea between the particles and expand the size of the pore throats.After imbibition by the fluid 14 and its solidification, the granularsolids and the nonvolatile liquid, or the water-soluble polymer, areleached out, leaving behind the larger pore throats. Much larger andlong throats may also be generated in the porous material, if thesolution is mixed by soluble fibers, or rod-like crystals. After theyare washed off, they leave behind large channels. Alternatively, if thefibers are insoluble, they reinforce the final matrix. Notably, such aprecise control on the pore space morphology of the material cannot beattained by conventional methods such as polymer precipitation throughcooling or by solvent evaporation. In the former case, the pore volumeof the material is controlled by the initial composition of thesolution, while the spatial distribution and size of the pores aredetermined by the rate of cooling. In the latter method, the porestructure is controlled by the rate of evaporation. However, evenprecise control of such factors generally does not provide any knowledgeon the size distributions of the pore bodies and pore throats;accordingly, they still have to be measured afterwards.

Experiments/Examples

Various experiments have been conducted to demonstrate the techniquesdescribed herein for producing composite materials and/or structured orporous materials. The experiments also demonstrate the flexibility ofthe disclosed techniques for producing various different materials. Adescription of the experiments and their findings are reported below.All experiments include: a step of making of the lattice construction 10(also referred to as a “cake”) and invading the construction 10 with afluid material 14. Optionally, at least a portion of the latticeconstruction 10 is later removed by dissolution or washing. Theconstructions 10 in these examples were prepared from particles aspurchased or further processed (e.g., milled, sieved, recrystallized,etc.) in order to have the desired particle size and/or particle sizedistribution. The materials used in these experiments are listed inTable 1 below.

TABLE 1 Supplier/ Short Grade/ Supplier/ Manufacturer Name Full NamePart No. Manufacturer Address Notes LLDPE1 Low Density Dowlex DowChemical 2030 Dow Center, Polyethylene 3010 Midland, MI 48674 TPXPolymethylpentene 1481T11 McMaster Carr 9630 Norwalk Blvd., Supply Co.Santa Fe Springs, CA 90670-2932 Nylon Nylon 0.48 gauge HoneywellPottsville, PA 17901 FEP Fluorinated 85905K64 McMaster Carr 9630 NorwalkBlvd., Ethylene Propylene Supply Co. Santa Fe Springs, CA 90670-2932 PSFPolysulfone Thermalux Westlake P.O. Box 127, Lenni, PlasticsPennsylvania Company Salt Sodium Chloride Table Salt Brand Chef's 3299E. Colorado Review/Smart Blvd., & Final Pasadena, CA 91107 Morton SodiumChloride EX FN 200 Morton Salt 123 North Wacker Salt Salt ConsumerDrive, Chicago, IL Products 60606-1743 Ryan Natural Ryon Flock RCEB2-Claremeont 107 Scott Drive, Fiber Fiber 0240-55D Flock Corp Leominster,MA 01453 Ag @ Silver Coated Glass Silglass 30- Technic 300 Park EastDrive, Glass Sphere 711 Engineered Woonsocket, Rhode Powders Island02895 Division Ag @ Cu Silver Coated Lot. No. Umicore Canada P.O. Box3538, Fort Average Copper Particles 92549 Inc. Saskatchewan AB T8LParticle ~3 um 2T4 Fe Feronyl Iron 1140150 International 1361 Alps Road,Specialty Wayne, New Jersey Products 07470 Cement Cement VersaBondCustom Building 13001 Seal Beach Dry Milled ~35 um Flex Products Blvd.,Seal Beach, CA Fortified 90740 Thin-Set Mortar SiC(g) Green Silicon Lot.No. Electro 701 Willet Road, 280 Mesh Carbide Powder 3233 AbrasivesCorp. Buffalo, NY 14218 IPA Isopropanol 20290 Ashland Inc. Los Angeles,CA 99% Purity 90074-3192 PG Propylene Glycol 9402-03 J. T. Baker/ 222Red School Lane, Mallinckrodt Phillipsburg NJ 08865 Baker, Inc. NylonNylon Mesh Mesh? Copper Copper Mesh 9224T816 McMaster Carr 9630 NorwalkBlvd., 100 Mesh Mesh Supply Co. Santa Fe Springs, CA 90670-2932 PPPolypropylene Surlyn Ionomer E. I. duPont de Wilmington, DE 19898Nemours & Co. HCl Hydrochloric acid 1N Epoxy Two-Part Epoxy Devcon 5-McMaster Carr 9630 Norwalk Blvd., Minute Supply Co. Santa Fe Springs, CAEpoxy 90670-2932

Materials Used for Preparation of Salt Cake

-   -   1. Chef's Review Plain Vacuum Granulated Table Salt with        Anti-caking agent Yellow Prussiate of Soda (cube size ˜350 μm)        (Los Angeles, Calif.)    -   2. 99% Isopropyl Alcohol    -   3. JT Baker Propylene Glycol (Phillipsburg, N.J.)    -   4. US Stoneware Cylindrical Ceramic Alumina Burundum Grinding        media ½ inch radius end cylinder (East Palestine, Ohio)    -   5. US Stoneware Roalox Jar 775-0 (Volume: 1.8 L) (East        Palestine, Ohio)    -   6. Carver Auto Series Automatic Hydraulic Press (Wabash, Ind.)    -   7. Paul N. Gardner Co. 8-path wet film applicator #25 and #14        (Pompano Beach, Fla.)    -   8. McMaster-Carr Polyester Felt Filter Bag 25 μm (Elmhurt, Ill.)    -   9. Davis Standard 2.5 inch diameter screw; length/diameter: 20        (Pawcatuck, Conn.)

Preparation of Slurry from Powder or Powder Mixture

As received powders were dispersed in a liquid medium (normally IPA) atapproximately 25 to 45 percent solids (volume basis) and mixedthoroughly and stored in sealed glass jars prior to usage.

Preparation of Salt Slurry by Ball Milling

Grinding media (ceramic balls) was placed in a jar mill to fill 45-55%of the jar capacity. About 1 kg of salt was poured into the jar alongwith enough IPA to cover the media by approximately 1 inch. The jar wasplaced on rollers at 235 rpm and the salt was milled for 7 days. Thesalt slurry formed was then diluted with additional IPA and filteredthrough a 25 μm filter. The filtered salt particles were then allowed tosettle and the IPA was decanted. Propylene Glycol was added to the saltresulting in salt slurry with 60% solids.

Preparation of Slurry Using an Attrition Mill

The slurry was also prepared by milling the as received powders in aliquid medium using an attrition mill (Union Process, Model 1S). In anexample formulation, 1 kg of dry salt (NaCl) was added to 0.538 kg ofIPA and milled using ¼″ ceramic balls for 15 minutes at 250 rpm. The ¼″ceramic balls were replaced by ⅛″ ceramic balls and the slurry wasmilled for another 15 minutes. The slurry was drained out and stored ina sealed glass jar for later use. FIG. 7 shows a typical particle sizedistribution of the salt slurry measured by light scattering using aHoriba Laser Scattering Particle Size Distribution Analyzer, ModelLA910.

Preparation of Fine Particles Using Dry Milling

Fine salt particles were also prepared using dry attrition milling. Theattrition mill was heated using hot water (150° F.) and maintained at140° F. to remove the moisture from the salt. 1 kg of dry salt was addedand milled using ¼″ ceramic balls for 30 minutes at 250 rpm. A stainlesssteel sieve (mesh 4, W.S. Tyler Corporation) was used to separate theceramic balls from dry salt powder. This resulted to a fine dry saltpowder with an average particle size of 18 microns measured by lightscattering using a Horiba Laser Scattering Particle Size DistributionAnalyzer, Model LA910. The dry powder was stored in a sealed glass jar.This powder was dispersed in IPA for further use as described earlier.

Preparation of Slurry Mixtures

As prepared slurry was mixed with different kinds of powders andthoroughly homogenized and stored in glass jar for later use.Experiments/Examples No. 11 and 12 are examples of this process.

Preparation of Lattice Construction/Cake from the Slurry

A lattice construction/cake was prepared by coating the slurry (<1000centipoise at 200 1/s) on a 0.0045″ thick siliconized paper (LoparexCo.) or 4-mil aluminum foil using Byrd bar (Gardco wet film applicator)at various wet thicknesses and dried in an oven at 70° C. for 1-10minute.

A lattice construction/cake was also prepared by directly coating thedry powder on a siliconized paper (Loparex Co.) and compacted using aroller.

Invasion of the Lattice Construction/Cake with a Molten Polymer

FIG. 8 shows a schematic of a typical set up used to execute theinvasion step in experiments with polymer melts. As shown, a polymericfilm (i.e., the material 14) was sandwiched between one or two latticeconstructions or cakes 10 and pressed with a prescribed temperature,pressure (or force), and dwell times using a heated press (in particulara Carver Press Auto Series—Auto Four/30—Model 3895). Siliconized paperwas used for the ease of handling of the lattice constructions. Astainless steel shim combined with silicone rubber was optionally usedto reduce cracking which may occur during the process. The experimentalconditions for various experiments/examples are given in the table shownin FIGS. 9A, 9B and 9C. Following pressing, the resulting compositematerial samples (i.e., corresponding to the composite materials 16)were cooled down. In the cases were the lattice constructions/cakes 10contained salt, the composite material samples were dipped in a largewater tank to remove most of the salt particles and subsequently dippedinto a second water beaker (for washing). The water temperature in thesecond beaker was controlled at 50° C. and the water was constantlyagitated with a magnetic stir bar for 5 min. The sample was heldperpendicular to the water circulation by a plastic comb. This wouldallow for the substantially complete dissolution of salt particlesinside. FIGS. 10 and 11 (from examples 1 and 2) show experimentalresults with poor and relatively complete washing, respectively.

Examples 3 and 4 represent the case were the original latticeconstruction (salt) was combined with Nylon and copper meshes. Thecombined lattice constructions (salt and mesh) were invaded with apolymer melt in the set up described above. The composite materialsamples were then washed in order to remove the salt particles. FIGS. 12and 13 are SEM images of the resulting material in cross-section.

Examples 5 through 8 illustrate different cases where the latticeconstruction 10 was made of various particulate materials such as metalpowders (iron and silver coated copper) and inorganic materials such assilicon carbide and cement (shown in FIGS. 14-17, 14A and 15A).

Examples 9, 13, 14, and 15 demonstrate various examples in which highperformance polymers (TPX, Nylon, FEP, and PSF) were processed accordingto the herein described method and the salt was completely extracted toform a porous matrix (shown in FIGS. 18, 22, 23, and 24).

In example 10, a TPX polymeric film was pressed between two dissimilarlattice constructions; one was made from milled salt, whereas the otherwas made from slurry of Morton salt in IPA. FIG. 19 shows the resultingdifferent pore structures on either side of the film.

In example 11 and 12 active fillers (Ryan fiber and silver coated glass)were incorporated into the final porous matrix. SEM images of theresulting materials as shown in FIGS. 20 and 21 in cross-section. As itis shown in FIG. 21, the silver coated glass spheres were trapped insidethe porous matrix but their surfaces (completely or partially) wereexposed to the pore volume.

Examples 16 through 20 show the results of the salt sieving experiments.The milled slurry was sequentially sieved through different mesh sizes(large to small) in order to fraction the salt particles in the ranges(>100, 80-100, 45-80, 25-45, <25 um). The fractioned slurries were usedto form the lattice constructions 10 and further invaded with moltenpolymer. FIGS. 25 through 29 show the cross-section SEM images of someof the final samples after extraction of the salt particles.

In example 21, the lattice construction was prepared from a salt slurrycontaining 5% propylene glycol and dried at 70° C. for 1 min. FIG. 30shows a cross-section SEM image of the final sample after extraction ofthe salt particles.

Examples 22 and 23 Preparation of Porous Polypropylene (PP)

A commercially available 2-mil polypropylene film was processed. FIG. 31shows a modified PP surface. The surface is clearly porous. For invasionof polypropylene into salt, temperatures at 300-400F (one-sided) andpressures at >50 psi are sufficient conditions for the invasion process.

Example 24 Preparation of Porous DuPont SURLYN Ionomer

DuPont SURLYN Ionomer pellets (DuPont, Wilmington, Del.) were extrudedat 440° F. at 2.5 mil with the back-up roll at 150° F. and the linespeed 30 ft/min. 10 mil wet salt slurry were coated on siliconized paperand dried for 7.5 minutes at 70° C. Two dried salt cake on thesiliconized paper were then inserted into the front and back of the nip(gap 8 mil) of the back-up rolls to sandwich the extruded ionomer as itwent through the nip of the rollers. The film was then washed and setout to dry. FIG. 32 shows a modified Ionomer surface. The porousstructure is clearly observed.

Example 25

Demonstrates the case where the lattice construction 10 was formed byfirst making of calcium carbonate slurry in water and coating the slurryon a siliconized paper. The coating was dried in an oven at 100° C. for5 min. and invaded with molten polymer (LLDPE1) using the same set updescribed above. The calcium carbonate powder was leached out using 1NHCI for 15 min. and the sample was dried in air. Top view andcross-section SEM images of this sample are shown in FIG. 33.

Example 26

Demonstrates the case where the lattice construction 10 was formed fromthe dry salt powder. The dry salt powder was obtained by wet milling thesalt and subsequently drying it at room temperature overnight. Theobtained chunks were re-grounded dry and spread over a siliconized paperand compacted to form a cake. The LLDPE1 film was pressed between twodry salt layer according to the conditions shown in FIG. 9. Afterwashing the porous sample obtained (see FIG. 34)

Example 27

This example demonstrates the case where a two-component epoxy materialused to invade the salt cake. The sample was allowed to cure and washedin order to remove the salt material (see FIG. 35).

Example 28

Demonstrates the case where the lattice construction 10 was formed byscreen printing a salt paste (milled salt 85%+propylene glycol 15%) overa siliconized paper. The salt was washed in order to create the porousregions (see FIGS. 36 and 37)

Example 29 Preparation of Porous Glycol-Modified PolyethyleneTerephthalate (PETG)

A piece of extruded glycol-modified polyethyleneterphatalate (PETG) filmwas sandwiched between two salt cakes in a hydraulic press. The plateswere set at 400° F. (one-sided) and the total sandwich was pressed for60 seconds at 60 psi. The sandwich was removed from the press to coolfor ˜1 minute and the film was washed with water to remove the salt andfinally set-out to air dry. FIG. 38 shows the top view of PETG afterbeing modified using the process described above. The surface is clearlyporous. FIG. 39 is the cross section view of PETG after being treated onboth surfaces. The pores are clearly connected.

It is to be appreciated that the proposed methods described herein haveseveral distinct advantages over previous methods, including but notlimited to the following:

-   -   (1) Since the porous material is prepared by invading the salt        layer or lattice construction, washing away the salt is easy, as        all the crystals are accessible through their contact with each        other. This is in contrast with methods of mixing salt and        polymer together which leaves many of salt crystals trapped in        the polymer structure.    -   (2) By selecting the appropriate particle shape and size        distribution for the lattice construction, precise control of        the pore morphology can be achieved. The pore size distribution        can be made very narrow for uniformity throughout the porous        material. The pore size can range from small as for the        applications related to microfiltration to large pores with        diameter in the range of millimeters. In one exemplary        embodiment, the pore size is 1 micron. In another rexemplary        embodiment, the pore size is 0.2 micron. In yet another        exemplary embodiment, the pore size is 500 microns.    -   (3) A graded porous structure, one in which there is a certain        gradient in the mean sizes of the pores in a given direction,        can easily be produced, which is advantageous for controlling        cross-flow filtration. For example, this can be done by using        several layers of salts, each made of a different crystal size        distribution. The graded salt structure can also be produced by        controlled drying of the layer. Generally, prior art methods        cannot produce such gradient pore structures.    -   (4) A bimodal, trimodal or even multi-modal pore structure        (i.e., having two or three or more distinct pore sizes) can be        generated straight forwardly, for example, by mixing different        granular solids having different particle-size distributions.    -   (5) Since the shapes of the pore bodies and pore throats are        controlled by those of the crystals and their contact area, a        large variety of pore shapes can be generated by using the        appropriate crystal shapes, and using easily washable materials        whose crystal structure has the desired shape.    -   (6) The porous material created using the process can be used as        filtration membranes, tissue scaffolding, wound healing,        microfluidics, medical diagnostics, artificial paper, make up        remover, etc. If the intended application of the porous material        is to be used as a membrane, one can generate a membrane for        active filtration, by embedding surface-active particles (SAPs)        in the salt. For example, the SAPs may be antibacterial agents,        catalyst particles (to induce a reaction), etc. Once the salt is        washed off, the SAPs remain in the porous medium.    -   (7) One can generate a given porous pattern on the surface and        in the bulk of the material by, for example, patterning the salt        layer. For example, the porous pattern can function as a        separation unit in a polymeric microfluidics device. Such        patterns can be highly useful to cross-flow filtration, as they        generate local turbulence in a fluid that is flowing over the        surface.    -   (8) Depending on the application, many microstructural patterns        in the bulk of the material may be produced. For example, if the        pores between the salt crystals are first filled with a high        viscosity fluid, such as propylene glycol (PG), then this fluid        is displaced by a low-viscosity, monomeric mixture which is        either completely or partially miscible with the PG in the salt        pore space. The monomeric mixture is then cured or polymerized        by heat or ultraviolet light. Then, the salt and the residual PG        are washed off, leaving behind the cured polymeric        microstructure. Clearly, depending on the viscosity contrast        between the PG and the monomeric mixture (and the wettability,        if the fluids are not miscible at all), a wide variety of        microstructures may be produced. Some of such structures are        branching without a significant number of close loops, while        others may have many closed loops.    -   (9) The porous surface may be made such that it is resistant to        fouling or the accumulation and deposition of living organisms        or non-living material on the surface of the porous material.    -   (10) The wettability of the surface can be controlled and        altered, using a variety of techniques involving surface        treatment. Modification of a surface structure, especially its        roughness, for controlling its wettability is a highly        desirable. Superhydrophobic and superoleophobic surfaces        (surfaces with contact angles larger than 150° and minimal        contact angle hysteresis) that do not absorb water and oil, as        well as surfaces that reduce drag can be created by changing the        structure of a surface. Micrometer-scale roughness on        hydrophobic surfaces increase the apparent contact angle and        subsequently retains a microscopic layer of air between water        and the surface—usually referred to as the Cassie-Baxter state        to create a superhydrophobic and superoleophobic surface. Water        drops on such superhydrophobic surfaces move with minimal        resistance.    -   (11) If binding or not binding to the porous surface is        important (e.g., in purification of proteins), then, the surface        can be created having permanent electrical charge of a given        sign. This can be accomplished by adding ionic species to        lattice construction 10, invading fluid 14 and/or other fluid        12.    -   (12) A large number of different thermoplastic or even thermoset        polymers may be used. In particular, in the case of a thermoset        polymer, the thermosetting reaction occurs within the pores of        the salt layer. Thus, one may use a polymer that would produce a        chemically and mechanically durable surface and membrane.    -   (13) The process can be used to create both thin and thick        porous materials with the desired porosity and pore size        distribution. For example, the thickness can be less than 0.01        inches, or less than 0.001 inches. On the other hand, the        thickness can be greater than 0.5 inches, or greater than 1        inch.    -   (14) When the invasion is conducted partially into the lattice        construction, the porous material created through this process        will have porosity on the surfaces the same as porosity in the        bulk of the material.

Interestingly, the resulting porous material 18 manufactured accordingto the presently disclosed method(s) may optionally acquiredadvantageous or otherwise desirable properties for particularapplications. For example, in one embodiment, the polymeric material 14can start out as a transparent film, and with treatment, it become anopaque material due to the voids created as a result of the presentlydisclosed processes. In addition, the polymeric film becomes thickerwith treatment as a result of the creation of voids which makes thematerial expand. In one example, the film increases in thickness from 55μm to 138 μm.

The percent transmittance of light through the film is also modified bythe process above. This can be seen in FIG. 40 where the percenttransmittance of light was measured by a Haze-Gard Plus from SheenInstruments. Notably, the percent transmittance decreases with anincrease in porous layer thickness of the modified porous material. Thiseffect is increased with decreased particle size of the solid templateor lattice construction. This effect is similarly seen in the clarity ofthe porous material as shown in FIG. 41. As the porous layer thicknessincreases, the clarity of the porous material decreases as well.Treatment of the film increased the haze of the porous material,however, it remained substantially constant with an increase in porouslayer thickness as seen in FIG. 42. Both haze and clarity were measuredby using the aforementioned Haze-Gard Plus.

In comparing the opacity of TiO2-containing film versus porous-treatedfilm produced in accordance with the presently disclosed methods, theabsorption coefficient was calculated using the Lambert-Beer law fromthe percent transmission data. It was found that the absorptioncoefficient is only slightly higher than TiO2-containing film for filmthat is treated with an approximate pore size of <5 μm.

The texture of the polymeric material can also be optionally modifiedwith treatment of the film as presently disclosed. The smaller theparticle size of the solid template or lattice construction, thesmoother and softer the modified film becomes.

Additionally, a polymeric untreated material can be modified to haveincreased hydrophilic or hydrophobic properties depending on itsmaterial properties. With the porous structure achieve via the presentlydisclosed treatment, the modified film can increase its affinity orrepulsion of water. For example, where the water contact angle was about90 degree on the untreated non-porous film and the water contact anglewas more than 150 degree as a result of the porous structure createdusing the methods disclosed herein.

Dowlex 3010 LLDPE from Dow in Midland, Mich. also shows a decrease inelasticity and a lower yield at low strain after being made porous inaccordance with the presently disclosed process. In this experiment, thestress-strain curves were measured using an Instron Model 5542.

In any event, it is to be appreciated that in connection with theparticular exemplary embodiment(s) presented herein certain steps andstructural or function features are described as being incorporated indefined elements and/or components. However, it is contemplated thatthese features may, to the same or similar benefit, also likewise beincorporated in other elements and/or components where appropriate. Itis also to be appreciated that different aspects of the exemplaryembodiments may be selectively employed as appropriate to achieve otheralternate embodiments suited for desired applications, the otheralternate embodiments thereby realizing the respective advantages of theaspects incorporated therein. Additionally, while described in a certainorder herein, it is to be appreciated that where appropriate the orderof steps may be altered.

Moreover, it is to be appreciated that certain elements described hereinas incorporated together may under suitable circumstances be stand-aloneelements or otherwise divided. Similarly, a plurality of particularfunctions described as being carried out by one particular element maybe carried out by a plurality of distinct elements acting independentlyto carry out individual functions, or certain individual functions maybe split-up and carried out by a plurality of distinct elements actingin concert. Alternately, some elements or components otherwise describedand/or shown herein as distinct from one another may be physically orfunctionally combined where appropriate.

In short, the present specification has been set forth with reference topreferred embodiments. Obviously, modifications and alterations willoccur to others upon reading and understanding the presentspecification. It is intended that the invention be construed asincluding all such modifications and alterations insofar as they comewithin the scope of the appended claims or the equivalents thereof.

1. A method of forming a composite material, comprising: (a) forming afirst lattice construction from a plurality of solid particles, saidconstruction being formed so as to have one or more gaps between theparticles, said gaps being at least partially filled with a first fluidmaterial; (b) partially displacing the first fluid material with aninvading fluid material such that the invading fluid material partiallypenetrates the gaps in the lattice construction; (c) at least partiallysolidifying the invading fluid material which penetrated the gaps in thelattice construction to form a composite material; and, (d) removing atleast a portion of the solid particles from the composite material,thereby forming at the location of the removed portion one or more poresin the solidified invading material.
 2. A method of forming a compositematerial comprising: (a) forming a first lattice construction from aplurality of solid particles, said construction being formed so as tohave one or more gaps between the particles, said gaps being at leastpartially filled with a first fluid material; (b) partially displacingthe first fluid material with an invading fluid material such that theinvading fluid material partially penetrates the gaps in the latticeconstruction; (c) at least partially solidifying the first fluidmaterial to form a composite material; and, (d) removing at least aportion of the solid particles from the composite material, therebyforming at the location of the removed portion one or more pores in thesolidified first material.
 3. The method of claim 1 or 2, wherein thecomposite material is a filtration membrane, tissue scaffold,microfluidics, medical diagnostics, artificial paper, or make upremover.
 4. The method of claim 1 or 2, wherein the pore sizedistribution is narrow.
 5. The method of claim 1 or 2, wherein the poresize is greater than 500 microns.
 6. The method of claim 1 or 2, whereinthe pore size is smaller than 1 micron.
 7. A composite material madefrom the method of claim 1 or 2, wherein the material is a sheet likematerial and has a first porosity on one surface, a second porosity onthe surface on the opposite side, and a bulk porosity, and the firstporosity, the second porosity and the bulk porosity are substantiallythe same.